"Indeed, this was approved, despite an indication that less impacting disposal alternatives may exist," the report pointed out.

More widely, it said that a long-term plan for sustainable development due to be completed by Australia by 2015 had to result in "concrete and consistent management measures sufficiently robust to ensure the overall conservation" of the reef.

In particular, it had to address major drivers of reef decline "such as water quality and climate change, and the need to constrain coastal development and associated activities".

"Given the range of significant threats affecting the property and the conflicting information about the effectiveness of recent decisions and draft policies, significant concern remains regarding the long-term deterioration of key aspects of... [the reef] and the completion of work to tackle short- and long-term threats," it said.

In the absence of "substantial progress", Unesco should consider putting the reef on the endangered list at a summit to be held in 2015, the report said.

Australia's Environment Minister Greg Hunt pointed out that the report highlighted progress in a number of areas, including water quality.

The approval of the Abbot Point development "was subject to rigorous environmental assessment", he said in a statement.

Queensland's Environment Minister Andrew Powell, meanwhile, said he was confident that ongoing work would mean the reef was not listed as endangered.

"We are committed to protecting the reef, we can continue to operate sensible, environmentally responsible ports adjacent to the reef," the Australian Broadcasting Corporation quoted him as saying.